While elemental liquid bromine is an effective biocide, its low solubility (&lt;4 g/100 g water), low boiling point (54.3.degree. C.), high vapor pressure (214 mm Hg at 25.degree. C.) and extreme corrosivity limit its use as a biocide in industrial applications. Another oxidizing bromine compound, bromine chloride, has slightly higher water solubility but is more volatile than elemental bromine. One other oxidizing bromine compound, bromate, is very toxic to mammals and is a suspected carcinogen. Nonoxidizing inorganic bromine compounds, such as bromide, have little or no antimicrobial activity.
A mixture of an aqueous bromine solution and a bromine stabilizer has been used to generate stable oxidizing bromine compounds for use as a biocide. An unstabilized aqueous bromine solution is very acidic, unstable and emits very pungent bromine fumes. The concentration of stabilized hypobromite solution that can be made from liquid bromine, however, has been limited due to the low solubility of bromine in water.
It has also been suggested that, in addition to a bromine stabilizer, an oxidizer, such as hypochlorite, be added to activate the bromide to hypobromite. After the completion of the conversion of bromide to hypobromite, the hypobromite is stabilized by the addition of a halogen stabilizer, such as sulfamate. While this is an improved process with a higher level of oxidizing halogen content (around 14% as Br.sub.2), this process still requires the separate step of synthesizing sodium hypobromite (NaOBr) as a bromine source. NaOBr is known to be very unstable and will rapidly disproportionate to bromide and bromate, both of which have little or no antimicrobial activity. In addition, because sodium hypochlorite (NaOCl) is used as an activation agent, the concentration of stabilized product is limited by the available concentration of NaOCl.
Also known are methods of generating bromine for on-site use. Such processes involve electrolytically converting bromate into active bromine compounds such as bromine, hypobromous acid, hypobromite ion and hydrogen tribromide under acidic conditions. However, because the above process generates bromine for on-site use, methods or measures for optimizing bromine stabilization are not addressed.
Therefore, methods of generating higher concentrations of stable oxidizing bromine formulations in a safer manner are needed.